I will report on the recent progress in the study of confining strings. I will argue that high energy scattering on the worldsheet naturally leads to integrable dynamics. I will present lattice measurements of glueball spins in $D=3$ gluodynamics supporting this statement. I will also describe an integrable relativisti $N$-body system arising in the high energy limit on the worldsheet in massive adjoint $D=2$ QCD. This system describes an $N$-particle subsector of a massless $T\bar{T}$-deformed fermion.
Sergei works at the interface of particle theory, cosmology and string theory. Among other topics he is interested in the physics of black holes, eternal inflation, long distance modifications of gravity. Most recently, Sergei's work was focused on the cosmological and astrophysical signatures of axion-like particles motivated by string theory. In particular, he is studying the intriguing possibility to use the ongoing observations of astrophysical black holes as a tool to discover such particles.